3-Methooy-4-hydroxy-phenylethylglycol (MHPG) is a major metabolite of norepinephrine which can be measured accurately in urine samples by a gas chromatographic assay. MHPG has been measured in urine from unmedicated and drug-treated depressed patients. The unmedicated patients had urinary MHPG levels similar to those cited in the literature. Neither clonidine nor tegretol had a significant effect on the amount of MHPG in the patients' urine.